A voltage-driven element is an element capable of performing a specific function using a driving voltage, and is widely used in various applications. In an example of the voltage-driven element, a voltage-driven switching element comprising an insulated gate is known. The voltage-driven switching element controls a current value based on a gate voltage (an example of the driving voltage) supplied to the insulated gate, and is used, e.g., in an inverter system that converts a direct current voltage to an alternating current voltage. A power semiconductor switching element that includes an IGBT (Insulated Gate Bipolar Transistor) and a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) can be given as an example of the voltage-driven switching element.
In order to drive this type of the voltage-driven element, a drive unit is connected to the voltage-driven element. The drive unit is configured to control the driving voltage supplied to the voltage-driven element. The drive unit can control the driving voltage based on a control signal that commands on/off of the voltage-driven element. The drive unit can also control the driving voltage based on a signal representing a driving state of the voltage-driven element, or a signal representing a state of the external environment.
In this type of the drive unit, development of a technique to generate a high precision driving voltage is desired. If the precision of the driving voltage generated by the drive unit is low, the driving conditions of the voltage-driven element must be set taking the precision of the driving voltage into consideration. Consequently, if the precision of the driving voltage is low, the voltage-driven element cannot be driven under optimal conditions. Consequently, problems such as an increase in a surge voltage of the voltage-driven element, or an increase in power loss of the voltage-driven element occur.
An example of the drive unit capable of generating a high precision driving voltage is taught in Japanese Patent Application Publication No. 2006-324963. This drive unit is characterized to generate the high precision driving voltage by a feedback control of the driving voltage supplied to the gate resistor of the voltage-driven element. Specifically, by comparing the driving voltage with a high precision reference voltage, the driving voltage is controlled based on the results of this comparison. Since this drive unit can generate the high precision driving voltage, it can provide useful results for many purposes.